One type of mass storage device is a disc drive data storage system. Disc drive data storage systems include, for example, one or more magnetic or optical storage discs. In disc drives which include multiple storage discs, the discs are mounted on a spindle for co-rotation about a central axis. Each disc surface has an associated head slider (or “head”) which includes a transducer for reading data from the disc surface. Data is stored on the disc surface in circular, concentric data tracks. A “cylinder” is the set of tracks (one per each disc surface) which have the same radius from the central axis.
The ever-increasing demand for storage capacity has driven significant increases in areal density growth rate. Compound areal density growth rate has been projected at sixty percent per year for years to come. High recording densities are possible only if adequate signal-to-noise ratios (SNR) are achievable. In current longitudinal recording systems, SNR improvements are achieved by reducing the grain size distribution and grain volume. However, this potentially results in thermally unstable grain magnetization and thermal decay of the written information over a span of time. Additionally, write field limitations are having a capping influence on further expansion of longitudinal recording areal densities.
Perpendicular magnetic recording technologies are expected to be widely employed in data storage systems in the near future. These perpendicular recording technologies are expected to reduce the above-described technical difficulties in the longitudinal recording field. However, there exists a different set of technical difficulties and maturity problems for perpendicular recording. Currently, there is no clear indication or agreement in the industry on the transition point (i.e., at what areal density) where longitudinal recording will be replaced by perpendicular recording. Thus, methods of expanding the life span of longitudinal recording during this transition period are needed. Further, techniques for increasing storage capacity are always needed, whether it be for longitudinal recording, perpendicular recording, or any other magnetic, optical or other recording technology.
Embodiments of the present invention provide solutions to these and/or other problems, and offer other advantages over the prior art.